Answer: v = -3
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Work Shown:
As you can see, we don't square both sides until the square root portion is fully isolated or on its own side. So it happens after we subtract 1 from both sides.
Technically, you are able to square both sides without first isolating the square root. But that would mean you'd have to use the FOIL rule and things would get a bit messier than they have to be. Not to mention that the square root term wouldn't fully go away (so you'd have to square again later down the line).
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Checking the answer:
Replace every copy of v with -3. Simplify both sides. We should end up with the same number on each side
The answer is confirmed.